/* ----------------------------------------------------------------------
 * Project:      CMSIS DSP Library
 * Title:        arm_conv_partial_q31.c
 * Description:  Partial convolution of Q31 sequences
 *
 * $Date:        18. March 2019
 * $Revision:    V1.6.0
 *
 * Target Processor: Cortex-M cores
 * -------------------------------------------------------------------- */
/*
 * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 (the License); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "arm_math.h"

/**
  @ingroup groupFilters
 */

/**
  @addtogroup PartialConv
  @{
 */

/**
  @brief         Partial convolution of Q31 sequences.
  @param[in]     pSrcA      points to the first input sequence
  @param[in]     srcALen    length of the first input sequence
  @param[in]     pSrcB      points to the second input sequence
  @param[in]     srcBLen    length of the second input sequence
  @param[out]    pDst       points to the location where the output result is written
  @param[in]     firstIndex is the first output sample to start with
  @param[in]     numPoints  is the number of output points to be computed
  @return        execution status
                   - \ref ARM_MATH_SUCCESS        : Operation successful
                   - \ref ARM_MATH_ARGUMENT_ERROR : requested subset is not in the range [0 srcALen+srcBLen-2]

  @remark
                   Refer to \ref arm_conv_partial_fast_q31() for a faster but less precise implementation of this function.
 */

arm_status arm_conv_partial_q31(
	const q31_t *pSrcA,
	uint32_t srcALen,
	const q31_t *pSrcB,
	uint32_t srcBLen,
	q31_t *pDst,
	uint32_t firstIndex,
	uint32_t numPoints)
{

#if defined(ARM_MATH_DSP)

	const q31_t *pIn1;                                   /* InputA pointer */
	const q31_t *pIn2;                                   /* InputB pointer */
	q31_t *pOut = pDst;                            /* Output pointer */
	const q31_t *px;                                     /* Intermediate inputA pointer */
	const q31_t *py;                                     /* Intermediate inputB pointer */
	const q31_t *pSrc1, *pSrc2;                          /* Intermediate pointers */
	q63_t sum;                                     /* Accumulator */
	uint32_t j, k, count, blkCnt, check;
	uint32_t blockSize1, blockSize2, blockSize3;    /* Loop counters */
	arm_status status;                             /* Status of Partial convolution */

#if defined (ARM_MATH_LOOPUNROLL)
	q63_t acc0, acc1, acc2;                        /* Accumulator */
	q31_t x0, x1, x2, c0;                          /* Temporary variables */
#endif

	/* Check for range of output samples to be calculated */
	if ((firstIndex + numPoints) > ((srcALen + (srcBLen - 1U)))) {
		/* Set status as ARM_MATH_ARGUMENT_ERROR */
		status = ARM_MATH_ARGUMENT_ERROR;
	} else {
		/* The algorithm implementation is based on the lengths of the inputs. */
		/* srcB is always made to slide across srcA. */
		/* So srcBLen is always considered as shorter or equal to srcALen */
		if (srcALen >= srcBLen) {
			/* Initialization of inputA pointer */
			pIn1 = pSrcA;

			/* Initialization of inputB pointer */
			pIn2 = pSrcB;
		} else {
			/* Initialization of inputA pointer */
			pIn1 = pSrcB;

			/* Initialization of inputB pointer */
			pIn2 = pSrcA;

			/* srcBLen is always considered as shorter or equal to srcALen */
			j = srcBLen;
			srcBLen = srcALen;
			srcALen = j;
		}

		/* Conditions to check which loopCounter holds
		 * the first and last indices of the output samples to be calculated. */
		check = firstIndex + numPoints;
		blockSize3 = ((int32_t)check > (int32_t)srcALen) ? (int32_t)check - (int32_t)srcALen : 0;
		blockSize3 = ((int32_t)firstIndex > (int32_t)srcALen - 1) ? blockSize3 - (int32_t)firstIndex + (int32_t)srcALen : blockSize3;
		blockSize1 = ((int32_t) srcBLen - 1) - (int32_t) firstIndex;
		blockSize1 = (blockSize1 > 0) ? ((check > (srcBLen - 1U)) ? blockSize1 :  numPoints) : 0;
		blockSize2 = (int32_t) check - ((blockSize3 + blockSize1) + (int32_t) firstIndex);
		blockSize2 = (blockSize2 > 0) ? blockSize2 : 0;

		/* conv(x,y) at n = x[n] * y[0] + x[n-1] * y[1] + x[n-2] * y[2] + ...+ x[n-N+1] * y[N -1] */
		/* The function is internally
		 * divided into three stages according to the number of multiplications that has to be
		 * taken place between inputA samples and inputB samples. In the first stage of the
		 * algorithm, the multiplications increase by one for every iteration.
		 * In the second stage of the algorithm, srcBLen number of multiplications are done.
		 * In the third stage of the algorithm, the multiplications decrease by one
		 * for every iteration. */

		/* Set the output pointer to point to the firstIndex
		 * of the output sample to be calculated. */
		pOut = pDst + firstIndex;

		/* --------------------------
		 * Initializations of stage1
		 * -------------------------*/

		/* sum = x[0] * y[0]
		 * sum = x[0] * y[1] + x[1] * y[0]
		 * ....
		 * sum = x[0] * y[srcBlen - 1] + x[1] * y[srcBlen - 2] +...+ x[srcBLen - 1] * y[0]
		 */

		/* In this stage the MAC operations are increased by 1 for every iteration.
		   The count variable holds the number of MAC operations performed.
		   Since the partial convolution starts from firstIndex
		   Number of Macs to be performed is firstIndex + 1 */
		count = 1U + firstIndex;

		/* Working pointer of inputA */
		px = pIn1;

		/* Working pointer of inputB */
		pSrc2 = pIn2 + firstIndex;
		py = pSrc2;

		/* ------------------------
		 * Stage1 process
		 * ----------------------*/

		/* The first stage starts here */
		while (blockSize1 > 0U) {
			/* Accumulator is made zero for every iteration */
			sum = 0;

#if defined (ARM_MATH_LOOPUNROLL)

			/* Loop unrolling: Compute 4 outputs at a time */
			k = count >> 2U;

			while (k > 0U) {
				/* x[0] * y[srcBLen - 1] */
				sum += (q63_t) * px++ * (*py--);

				/* x[1] * y[srcBLen - 2] */
				sum += (q63_t) * px++ * (*py--);

				/* x[2] * y[srcBLen - 3] */
				sum += (q63_t) * px++ * (*py--);

				/* x[3] * y[srcBLen - 4] */
				sum += (q63_t) * px++ * (*py--);

				/* Decrement loop counter */
				k--;
			}

			/* Loop unrolling: Compute remaining outputs */
			k = count % 0x4U;

#else

			/* Initialize k with number of samples */
			k = count;

#endif /* #if defined (ARM_MATH_LOOPUNROLL) */

			while (k > 0U) {
				/* Perform the multiply-accumulate */
				sum += (q63_t) * px++ * (*py--);

				/* Decrement loop counter */
				k--;
			}

			/* Store the result in the accumulator in the destination buffer. */
			*pOut++ = (q31_t)(sum >> 31);

			/* Update the inputA and inputB pointers for next MAC calculation */
			py = ++pSrc2;
			px = pIn1;

			/* Increment MAC count */
			count++;

			/* Decrement loop counter */
			blockSize1--;
		}

		/* --------------------------
		 * Initializations of stage2
		 * ------------------------*/

		/* sum = x[0] * y[srcBLen-1] + x[1] * y[srcBLen-2] +...+ x[srcBLen-1] * y[0]
		 * sum = x[1] * y[srcBLen-1] + x[2] * y[srcBLen-2] +...+ x[srcBLen] * y[0]
		 * ....
		 * sum = x[srcALen-srcBLen-2] * y[srcBLen-1] + x[srcALen] * y[srcBLen-2] +...+ x[srcALen-1] * y[0]
		 */

		/* Working pointer of inputA */
		if ((int32_t)firstIndex - (int32_t)srcBLen + 1 > 0) {
			pSrc1 = pIn1 + firstIndex - srcBLen + 1;
		} else {
			pSrc1 = pIn1;
		}
		px = pSrc1;

		/* Working pointer of inputB */
		pSrc2 = pIn2 + (srcBLen - 1U);
		py = pSrc2;

		/* count is index by which the pointer pIn1 to be incremented */
		count = 0U;

		/* -------------------
		 * Stage2 process
		 * ------------------*/

		/* Stage2 depends on srcBLen as in this stage srcBLen number of MACS are performed.
		 * So, to loop unroll over blockSize2,
		 * srcBLen should be greater than or equal to 4 */
		if (srcBLen >= 4U) {
#if defined (ARM_MATH_LOOPUNROLL)

			/* Loop unroll over blkCnt */
			blkCnt = blockSize2 / 3;

			while (blkCnt > 0U) {
				/* Set all accumulators to zero */
				acc0 = 0;
				acc1 = 0;
				acc2 = 0;

				/* read x[0], x[1] samples */
				x0 = *px++;
				x1 = *px++;

				/* Apply loop unrolling and compute 3 MACs simultaneously. */
				k = srcBLen / 3;

				/* First part of the processing with loop unrolling.  Compute 3 MACs at a time.
				 ** a second loop below computes MACs for the remaining 1 to 2 samples. */
				do {
					/* Read y[srcBLen - 1] sample */
					c0 = *(py);

					/* Read x[2] sample */
					x2 = *(px);

					/* Perform the multiply-accumulate */
					/* acc0 +=  x[0] * y[srcBLen - 1] */
					acc0 += (q63_t) x0 * c0;
					/* acc1 +=  x[1] * y[srcBLen - 1] */
					acc1 += (q63_t) x1 * c0;
					/* acc2 +=  x[2] * y[srcBLen - 1] */
					acc2 += (q63_t) x2 * c0;

					/* Read y[srcBLen - 2] sample */
					c0 = *(py - 1U);

					/* Read x[3] sample */
					x0 = *(px + 1U);

					/* Perform the multiply-accumulate */
					/* acc0 +=  x[1] * y[srcBLen - 2] */
					acc0 += (q63_t) x1 * c0;
					/* acc1 +=  x[2] * y[srcBLen - 2] */
					acc1 += (q63_t) x2 * c0;
					/* acc2 +=  x[3] * y[srcBLen - 2] */
					acc2 += (q63_t) x0 * c0;

					/* Read y[srcBLen - 3] sample */
					c0 = *(py - 2U);

					/* Read x[4] sample */
					x1 = *(px + 2U);

					/* Perform the multiply-accumulate */
					/* acc0 +=  x[2] * y[srcBLen - 3] */
					acc0 += (q63_t) x2 * c0;
					/* acc1 +=  x[3] * y[srcBLen - 2] */
					acc1 += (q63_t) x0 * c0;
					/* acc2 +=  x[4] * y[srcBLen - 2] */
					acc2 += (q63_t) x1 * c0;


					px += 3U;

					py -= 3U;

				} while (--k);

				/* If the srcBLen is not a multiple of 3, compute any remaining MACs here.
				 ** No loop unrolling is used. */
				k = srcBLen - (3 * (srcBLen / 3));

				while (k > 0U) {
					/* Read y[srcBLen - 5] sample */
					c0 = *py--;
					/* Read x[7] sample */
					x2 = *px++;

					/* Perform the multiply-accumulates */
					/* acc0 +=  x[4] * y[srcBLen - 5] */
					acc0 += (q63_t) x0 * c0;
					/* acc1 +=  x[5] * y[srcBLen - 5] */
					acc1 += (q63_t) x1 * c0;
					/* acc2 +=  x[6] * y[srcBLen - 5] */
					acc2 += (q63_t) x2 * c0;

					/* Reuse the present samples for the next MAC */
					x0 = x1;
					x1 = x2;

					/* Decrement the loop counter */
					k--;
				}

				/* Store the result in the accumulator in the destination buffer. */
				*pOut++ = (q31_t)(acc0 >> 31);
				*pOut++ = (q31_t)(acc1 >> 31);
				*pOut++ = (q31_t)(acc2 >> 31);

				/* Increment the pointer pIn1 index, count by 3 */
				count += 3U;

				/* Update the inputA and inputB pointers for next MAC calculation */
				px = pSrc1 + count;
				py = pSrc2;

				/* Decrement loop counter */
				blkCnt--;
			}

			/* Loop unrolling: Compute remaining outputs */
			blkCnt = blockSize2 - 3 * (blockSize2 / 3);

#else

			/* Initialize blkCnt with number of samples */
			blkCnt = blockSize2;

#endif /* #if defined (ARM_MATH_LOOPUNROLL) */

			while (blkCnt > 0U) {
				/* Accumulator is made zero for every iteration */
				sum = 0;

#if defined (ARM_MATH_LOOPUNROLL)

				/* Loop unrolling: Compute 4 outputs at a time */
				k = srcBLen >> 2U;

				while (k > 0U) {
					/* Perform the multiply-accumulates */
					sum += (q63_t) * px++ * (*py--);
					sum += (q63_t) * px++ * (*py--);
					sum += (q63_t) * px++ * (*py--);
					sum += (q63_t) * px++ * (*py--);

					/* Decrement loop counter */
					k--;
				}

				/* Loop unrolling: Compute remaining outputs */
				k = srcBLen % 0x4U;

#else

				/* Initialize blkCnt with number of samples */
				k = srcBLen;

#endif /* #if defined (ARM_MATH_LOOPUNROLL) */

				while (k > 0U) {
					/* Perform the multiply-accumulate */
					sum += (q63_t) * px++ * *py--;

					/* Decrement loop counter */
					k--;
				}

				/* Store the result in the accumulator in the destination buffer. */
				*pOut++ = (q31_t)(sum >> 31);

				/* Increment MAC count */
				count++;

				/* Update the inputA and inputB pointers for next MAC calculation */
				px = pSrc1 + count;
				py = pSrc2;

				/* Decrement loop counter */
				blkCnt--;
			}
		} else {
			/* If the srcBLen is not a multiple of 4,
			 * the blockSize2 loop cannot be unrolled by 4 */
			blkCnt = (uint32_t) blockSize2;

			while (blkCnt > 0U) {
				/* Accumulator is made zero for every iteration */
				sum = 0;

				/* srcBLen number of MACS should be performed */
				k = srcBLen;

				while (k > 0U) {
					/* Perform the multiply-accumulate */
					sum += (q63_t) * px++ * *py--;

					/* Decrement loop counter */
					k--;
				}

				/* Store the result in the accumulator in the destination buffer. */
				*pOut++ = (q31_t)(sum >> 31);

				/* Increment the MAC count */
				count++;

				/* Update the inputA and inputB pointers for next MAC calculation */
				px = pSrc1 + count;
				py = pSrc2;

				/* Decrement the loop counter */
				blkCnt--;
			}
		}


		/* --------------------------
		 * Initializations of stage3
		 * -------------------------*/

		/* sum += x[srcALen-srcBLen+1] * y[srcBLen-1] + x[srcALen-srcBLen+2] * y[srcBLen-2] +...+ x[srcALen-1] * y[1]
		 * sum += x[srcALen-srcBLen+2] * y[srcBLen-1] + x[srcALen-srcBLen+3] * y[srcBLen-2] +...+ x[srcALen-1] * y[2]
		 * ....
		 * sum +=  x[srcALen-2] * y[srcBLen-1] + x[srcALen-1] * y[srcBLen-2]
		 * sum +=  x[srcALen-1] * y[srcBLen-1]
		 */

		/* In this stage the MAC operations are decreased by 1 for every iteration.
		   The blockSize3 variable holds the number of MAC operations performed */
		count = srcBLen - 1U;

		/* Working pointer of inputA */
		pSrc1 = (pIn1 + srcALen) - (srcBLen - 1U);
		px = pSrc1;

		/* Working pointer of inputB */
		pSrc2 = pIn2 + (srcBLen - 1U);
		py = pSrc2;

		/* -------------------
		 * Stage3 process
		 * ------------------*/

		while (blockSize3 > 0U) {
			/* Accumulator is made zero for every iteration */
			sum = 0;

#if defined (ARM_MATH_LOOPUNROLL)

			/* Loop unrolling: Compute 4 outputs at a time */
			k = count >> 2U;

			while (k > 0U) {
				/* sum += x[srcALen - srcBLen + 1] * y[srcBLen - 1] */
				sum += (q63_t) * px++ * *py--;

				/* sum += x[srcALen - srcBLen + 2] * y[srcBLen - 2] */
				sum += (q63_t) * px++ * *py--;

				/* sum += x[srcALen - srcBLen + 3] * y[srcBLen - 3] */
				sum += (q63_t) * px++ * *py--;

				/* sum += x[srcALen - srcBLen + 4] * y[srcBLen - 4] */
				sum += (q63_t) * px++ * *py--;

				/* Decrement loop counter */
				k--;
			}

			/* Loop unrolling: Compute remaining outputs */
			k = count % 0x4U;

#else

			/* Initialize blkCnt with number of samples */
			k = count;

#endif /* #if defined (ARM_MATH_LOOPUNROLL) */

			while (k > 0U) {
				/* Perform the multiply-accumulate */
				/* sum +=  x[srcALen-1] * y[srcBLen-1] */
				sum += (q63_t) * px++ * *py--;

				/* Decrement loop counter */
				k--;
			}

			/* Store the result in the accumulator in the destination buffer. */
			*pOut++ = (q31_t)(sum >> 31);

			/* Update the inputA and inputB pointers for next MAC calculation */
			px = ++pSrc1;
			py = pSrc2;

			/* Decrement MAC count */
			count--;

			/* Decrement the loop counter */
			blockSize3--;
		}

		/* Set status as ARM_MATH_SUCCESS */
		status = ARM_MATH_SUCCESS;
	}

	/* Return to application */
	return (status);

#else
	/* alternate version for CM0_FAMILY */

	const q31_t *pIn1 = pSrcA;                           /* InputA pointer */
	const q31_t *pIn2 = pSrcB;                           /* InputB pointer */
	q63_t sum;                                     /* Accumulator */
	uint32_t i, j;                                 /* Loop counters */
	arm_status status;                             /* Status of Partial convolution */

	/* Check for range of output samples to be calculated */
	if ((firstIndex + numPoints) > ((srcALen + (srcBLen - 1U)))) {
		/* Set status as ARM_MATH_ARGUMENT_ERROR */
		status = ARM_MATH_ARGUMENT_ERROR;
	} else {
		/* Loop to calculate convolution for output length number of values */
		for (i = firstIndex; i <= (firstIndex + numPoints - 1); i++) {
			/* Initialize sum with zero to carry on MAC operations */
			sum = 0;

			/* Loop to perform MAC operations according to convolution equation */
			for (j = 0U; j <= i; j++) {
				/* Check the array limitations */
				if (((i - j) < srcBLen) && (j < srcALen)) {
					/* z[i] += x[i-j] * y[j] */
					sum += ((q63_t) pIn1[j] * pIn2[i - j]);
				}
			}

			/* Store the output in the destination buffer */
			pDst[i] = (q31_t)(sum >> 31U);
		}

		/* Set status as ARM_MATH_SUCCESS */
		status = ARM_MATH_SUCCESS;
	}

	/* Return to application */
	return (status);

#endif /* #if !defined(ARM_MATH_CM0_FAMILY) */

}

/**
  @} end of PartialConv group
 */
